Tiêu đề 16. RADIATION POISONING.pdf ✅

PHARMD GURU Page 1 Radiation is defined as the energy given off by atoms in form of particles or electromagnetic rays. Most radio-contrast agents in use are iodinated contrast material which may be ionic or non-ionic compounds. 1. Ionizing radiation: radiation that has enough energy to remove electrons from atoms which convert to ions in form of particles or rays (particles, g-rays, x-rays). 2. Non-ionizing radiation: radiation that gives off enough energy to make atoms vibrate, however not enough energy to remove electrons (ex: radio waves, visible light, microwaves). USES:  Urography: The agents used for urography comprise mainly small molecule, water soluble, low protein binding, high plasma concentration compounds which are given IV. Ex: diatrizoates, iothalamates and metrizoates.  Angiography: These agents are water soluble, with low viscocity and radiodensity. Ex: Non-ionic monomers: iohexol.  Contrast radiography of GI tract: These are nonabsorbable agents which form a homogenous coat on the GI mucosa and do not interact with GI secretions. Ex: Barium sulfate.  Computerised tomography of GI tract: These are nonabsorbable iodinated water- soluble agents with high osmolality. Ex: Diatrizoate  Myelography: Agents for this are non-ionic, water soluble, and miscible with CSF. Ex: Metrizamide, iotralan.  Lymphography, lymphangiography: These agents are waterinsoluble with high radiodensity. Ex: Iodised oil, iotasol.  Magnetic resonance imaging: Gadolinium, manganese, and iron RADIATION POISONING
PHARMD GURU Page 2  Cholecystography, cholangiography: These agents are preferentially excreted in the bile after absorption from GI tract. Ex: Ipodates, iocetamic acid. MECHANISM: Radiation poisoning can be caused due to Localized Exposure from direct handling or Whole Body Exposure. Radiation can damage DNA, RNA, and proteins directly, but more often the damage to these molecules is indirect, caused by highly reactive free radicals generated by radiation's interaction with intracellular water molecules. Large doses of radiation can cause cell death, and lower doses may interfere with cellular proliferation. Damage to other cellular components can result in progressive tissue hypoplasia, atrophy, and eventually fibrosis. CLINICAL (TOXIC) SYMPTOMS:  Development of radiation burns (look like thermal burns); erythema, desquamation, blistering, appear over a period of days. Extent of localized injury is dependent on extent of penetration of radiation.  Inadvertent administration of ionic contrast agents such as diatrizoate or iodamine, instead of iopanidol, by the intrathecal route, has resulted in fatalities.  Gastrointestinal syndrome (death of intestinal mucosal cells).  Maximal leukopenia and thrombocytopenia occurs several weeks after exposure - hemorrhage and infection can be major problems at this time.  Long term sequelae of radiation exposure relates to the chance event of chromosomal injury.  Cardiovascular collapse and central nervous system damage with symptoms of lethargy, tremor, seizure, ataxia and death in 24-72 hours.  Death usually follows due to radiation pneumonitis, denudation of the alimentary tract, hepatic and renal dysfunction.
PHARMD GURU Page 3 INVESTIGATIONS/DIAGNOSIS: When a person has experienced known or probable exposure to a high dose of radiation from an accident or attack, medical personnel take a number of steps to determine the absorbed radiation dose. This information is essential for determining how severe the illness is likely to be, which treatments to use and whether a person is likely to survive.  Vomiting and other symptoms: The time between radiation exposure and the onset of vomiting is a fairly accurate screening tool to estimate absorbed radiation dose.  Blood tests: Frequent blood tests over several days enable medical personnel to look for drops in disease-fighting white blood cells and abnormal changes in the DNA of blood cells. These factors indicate the degree of bone marrow damage, which is determined by the level of an absorbed dose.  Dosimeter: A device called a dosimeter can measure the absorbed dose of radiation but only if it was exposed to the same radiation event as the affected person.  Survey meter: A device such as a Geiger counter can be used to survey people to determine the body location of radioactive particles. MANAGEMENT:  Prophylactic Drugs against Radiation Exposure: Amifostine and Androstenediol. Patients with a history of radiocontrast medium-related oedema should be given prophylactic corticosteroids.  Decontamination is accomplished by removing clothing and using soap and water — be careful not to abrade skin.  A wound that is contaminated should be copiously irrigated with saline.  Any person who reports nausea, vomiting, diarrhea should be taken to the hospital for evaluation of whole body exposure.  Chelators can be used for appropriate metals; Ca-DTPA (diethylene-diamine-penta- acetic acid) has been used for the actinide series (transuranics plutonium, neptunium, americium).  Prussian blue should be considered for cesium, thallium, and rubidium exposures.
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